Home's first-run line doesn't say the words land where the cursor is, or that the window needn't be open

## What happens

On a new install with no dictations, the Home page subtitle comes from `HomePresenter.subtitle` (`Sources/UttrflowUX/HomePresentation.swift:445`) and reads "Nothing dictated yet. Hold the shortcut anywhere and talk."

#368 removed a second "Try it now" card that repeated this line. That card was the only place on Home that said two things a new user needs: the text is typed wherever the cursor is, in any app, and the Uttrflow window does not need to be open. The pull request noted that if this matters, it belongs in the hero line, not in another card.

## Why it matters

"Anywhere" is ambiguous on a page inside the app's own window. A first-time user can reasonably think they should dictate into Uttrflow.

## How to check

Read line 445 and the two tests that pin the sentence: `Tests/UttrflowUXTests/HomePresentationTests.swift:104` and `:167`.

## Acceptance criteria

- The empty-history subtitle says, in one or two short sentences, that the words go where the cursor is in any app, and that this window can stay closed. Keep the product's plain tone (look at the other subtitles in the same function).
- Only the empty-history case changes; the blocked, today and earlier cases stay as they are.
- Both tests are updated, and the sentence still fits the hero (check `make app` and open Home, or say in the pull request that you could not run the app).

## Where to start

- `Sources/UttrflowUX/HomePresentation.swift:441-450`
- Tests to extend: `Tests/UttrflowUXTests/HomePresentationTests.swift`.
- Before pushing, run `make verify` (export DEVELOPER_DIR=/Applications/Xcode.app/Contents/Developer first). It is the same command CI runs, and it enforces the 95% coverage floor per module.
- Read [CONTRIBUTING.md](https://github.com/uttrflow/uttrflow-swift/blob/main/CONTRIBUTING.md) first, and say on this issue that you are taking it.

**Size:** XS to S, about 1 hour.

Read CONTRIBUTING.md, then inspect the empty-history branch in Sources/UttrflowUX/HomePresentation.swift:441-450 and the two expectations at Tests/UttrflowUXTests/HomePresentationTests.swift:104 and :167. Update only that subtitle case so it explains cursor placement in any app and that the window can stay closed, while the other cases remain unchanged. Run make verify with the specified Xcode developer directory and check the hero with make app if possible.

Written by the indexing model from the issue text.